Why do the epigenetic changes last only a few generations? Hmmm. Well, if life, in general, exists by design and not by chance, many adaptations may only be intended to last a few generations. Environments constantly change, after all, and a requirement that all patterns be locked in could be a road to extinction.
From ScienceDaily: For many years, it was thought that sperm do not retain any histone packaging and therefore could not transmit histone-based epigenetic information to offspring. Recent studies, however, have shown that about 10 percent of histone packaging is retained in both human and mouse sperm. “Furthermore, where the chromosomes retain histone packaging of DNA […]